work with file in c

/* এই কাজ করার আগে আপনাকে অবশ্যয় input.txt এবং output.txt ফাইল তৈরি করে নিতে হবে । 
input.txt ফাইল থাকতেই হবে না থাকলে এঁরর দিবে ।  output.txt না থাকলে তৈরি করে নিবে 
*/

int main()
{
  FILE *inputFile, *outputFile;
  inputFile = fopen("inputa.txt", "r");  // r for read
  outputFile = fopen("output.txt", "w"); // w for write
  if (inputFile == NULL)
  {
    printf("file not exist\n");
    return 0;
  }
  // char ch = fgetc(inputFile);
  // printf("%c\n", ch);
  // char ch2 = fgetc(inputFile);
  // printf("%c\n", ch2);
  // char ch3 = fgetc(inputFile);
  // printf("%c\n", ch3);
  // char ch4 = fgetc(inputFile);
  // printf("%c\n", ch4);

  while (1)
  {
    char ch = fgetc(inputFile);
    EOF; // it's end of file
    if (ch == EOF)
    {
      break;
    }
    fputc(ch, outputFile);

    printf("%c", ch);
  }
}
//=======read data from file and write this fata to output file==========
int main()
{
  FILE *inputFile, *outputFile;
  inputFile = fopen("input.txt", "r");
  outputFile = fopen("output.txt", "w");
  if (inputFile == NULL)
  {
    printf("file not found");
    fprintf(outputFile, "input file not found");
    return 0;
  }
  int n;
  fscanf(inputFile, "%d", &n);
  int sum = 0;
  for (int i = 0; i < n; i++)
  {
    int a;
    fscanf(inputFile, "%d", &a);
    sum += a;
  }
  fprintf(outputFile, "sum = %d\n", sum);
}

// =================== make log file
int main(){
  FILE *inputFile, *logfile;
  inputFile = fopen("input.txt", "r");
  logfile = fopen("log.txt", "a"); // a mean আগে ডাটা রেখে দিয়ে পড়ের গুলা অ্যাড করবে 
  fprintf(logfile,"hello");
   if(inputFile == NULL){
      fprintf(logfile,"input file not found at 12:00 AM\n");
      return 0;
    }
}